private static Assembly AssemblyResolveEventHandler(object sender, ResolveEventArgs args)
{
// If the assembly that caused this callback is not one of the assemblies packaged with this library, we do nothing:
if (args == null || args.Name == null)
{
return(null);
}
PackagedAssemblyLookup packagedAssemblies = GetPackagedAssemblies();
if (false == packagedAssemblies.TryFind(args.Name, out PackagedAssemblyLookup.Entry packagedAssemblyInfo))
{
return(null);
}
// Ok, we need to do stuff.
// If we already marked this assembly as processed, we are in a recursive call caused by the load request below.
// That means load failed even after copy and there is nothing else we can do.
if (packagedAssemblyInfo.IsProcessedFromPackage)
{
Log.Error(LogComonentMoniker, $"The assembly \"{args.Name}\" was not found using the normal assembly resolution method."
+ $" A fallback assembly binary is included in file \"{packagedAssemblyInfo.AssemblyFilePath}\"."
+ $" Copying that file into this application's base directory was attempted, but the assembly still cannot be resolved."
+ $" Giving up.");
return(null);
}
Log.Info(LogComonentMoniker, $"The assembly \"{args.Name}\" was not found using the normal assembly resolution method."
+ $" A fallback assembly binary is included in file \"{packagedAssemblyInfo.AssemblyFilePath}\"."
+ $" That file will be now copied into this application's base directory and the loading will be retried.");
// Validate AppDomain parameter:
Validate.NotNull(sender, nameof(sender));
AppDomain senderAppDomain = sender as AppDomain;
if (senderAppDomain == null)
{
throw new ArgumentException($"The specified {nameof(sender)} is expected to be of runtime type {nameof(AppDomain)},"
+ $" but the actual type is {sender.GetType().FullName}.");
}
CopyFileToBaseDirectory(packagedAssemblyInfo.AssemblyFilePath, senderAppDomain);
packagedAssemblyInfo.IsProcessedFromPackage = true;
Log.Info(LogComonentMoniker, $"Assembly binary copied into this application's base directory. Requesting to load assembly \"{packagedAssemblyInfo.AssemblyName}\".");
#if NETCOREAPP
Assembly resolvedAssembly = AssemblyLoadContext.Default.LoadFromAssemblyName(packagedAssemblyInfo.AssemblyName);
#else
Assembly resolvedAssembly = Assembly.Load(packagedAssemblyInfo.AssemblyName);
#endif
return(resolvedAssembly);
}
private static PackagedAssemblyLookup GetPackagedAssemblies()
{
PackagedAssemblyLookup packagedAssemblies = s_packagedAssemblies;
if (packagedAssemblies == null)
{
packagedAssemblies = ReadPackagedAssembliesFromDisk();
packagedAssemblies = Concurrent.TrySetOrGetValue(ref s_packagedAssemblies, packagedAssemblies);
}
return(packagedAssemblies);
}
private static PackagedAssemblyLookup ReadPackagedAssembliesFromDisk()
{
string packagedAssembliesDirectory = GetPackagedAssembliesDirectory();
var packagedAssemblies = new PackagedAssemblyLookup();
if (!Directory.Exists(packagedAssembliesDirectory))
{
Log.Error(LogComonentMoniker, $"Could not read any packaged assemblies from disk becasue the directory \"{packagedAssembliesDirectory}\" does not exist.");
return(packagedAssemblies);
}
foreach (string packagedFilePath in Directory.GetFiles(packagedAssembliesDirectory, "*.dll", SearchOption.AllDirectories))
{
if (TryGetAssemblyName(packagedFilePath, out AssemblyName assemblyName))
{
var packagedAssembly = new PackagedAssemblyLookup.Entry(assemblyName, packagedFilePath);
packagedAssemblies.Add(packagedAssembly);
}
}
Log.Info(LogComonentMoniker, $"Read {packagedAssemblies.Count} packaged assemblies from \"{packagedAssembliesDirectory}\".");
return(packagedAssemblies);
}